Driving home and all of a sudden my fuel gauge starts from half tank and moving to full mark. It will go back and forth like its getting surges of power or something. Is it a broken wire grounding out or the sending unit going out?? When I fill up it will go to the 3 o'clock position. Driving down the road it'll go back and forth from where it used to be and 3' o clock position. Did have a fuse blow cause of wire grounding to my brake lights but fixed that prob.